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How  lo  install  electric! 
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and  alarms 


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HOW  TO  INSTALL 

qtriq  Bells, 

2lNNUN@m  TORS, 

and  Alarms. 

INCLUDING 


tteries.  Wires  and  Wiring,  Circuits,  Pushes,  Bells,  E 
Alarms,  High  and  Low  Water  Alarms,  Fire  Alarms, 
Thermostats,  Annunciators,  and  the  Location 
and  Remedying  of  Troubles. 


By  NORMAN  H.  SCHNEIDER 


LEARN  TO  DO  THINGS 


Model  Library  Series 

OF  COPYRIGHTED  BOOKS 

1.  The  Study  of  Electricity  for  Beginners, 

2.  Dry  Batteries,  How  to  Make  them. 

3.  Electrical  Circuits  and  Diagrams,  Part  1. 

4.  Electric  Bells,  Annunciators  and  Alarms. 

5.  Modern  Primary  Batteries. 

6.  Experimenting  with  Induction  Coils. 

7.  Electric  Gas  Igniting  Apparatus. 

8.  Small  Accumulators,  How  to  Make  and  Use 

9.  Model  Steam  Engine  Design. 

10.  Practical  Electrics. 

1 1.  Inventions,  How  to  Protect  and  Sell  them. 

12.  Woodwork  Joints,  How  to  Make  and  Use. 

13.  The  Fireman’s  Guide  to  the  Care  of  Boilers 

14.  The  Slide  Valve  Simply  Explained. 

15.  The  Magneto  Telephone. 

16.  The  Corliss  Engine  and  Its  Management. 

17.  Making  Wireless  Outfits. 

18.  Wireless  Telephone  Construction. 

19.  The  Wimshurst  Machine,  How  to  Make  It. 

20.  Simple  Experiments  in  Static  Electricity. 

21.  Small  Electrical  Measuring  Instruments. 

22.  Electrical  Circuits  and  Diagrams,  Part  2. 

23.  Induction  Coils,  How  to  Make  Them. 

24.  Model  Vaudeville  Theatres, 

25.  Alternating  Currents,  Simply  Explained. 

26.  How  to  Build  a 20  foot  Bi-plane  Glider. 

27.  A B C of  the  Steam  Engine. 

28.  Simple  Soldering,  Hard  and  Soft. 

29.  Telegraphy  for  Beginners. 

30.  Low  Voltage  Lighting  with  Storage  Batteri  es 

33.  House  Wiring  for  Electric  Light. 

34.  Magnets  and  Magnetism. 

36.  Small  Windmills  and  How  to  Make  Therm 

31.  Lieckfield  Gas  and  Oil  Engines. 

37.  Collin's  Wireless  Plans,  Part  1. 

38.  Collin’s  Wireless  Plans,  Part  2. 

IN  PAPER  COVERS 

PRICE  35  CENTS  EACH 


HOW  TO  INSTALL 

Electric  Bells,  Annunciators, 
and  Alarms. 


INCLUDING 

Batteries , Wires  and  Wiring,  Circuits,  Pushes,  Bells , 
Burglar  Alarms,  High  and  Low  Water  Alarms, 
Fire  Alarms,  Thermostats,  Annunciators , 
and  the  Locatio?i  and  Remedying 
of  Troubles . 


BIv 

NORMAN  HT  SCHNEIDER, 

Author  of  “The  Study  of  Electricity  for  Beginners,”  “Care  and 
Handling  of  Electric  Plants,”  etc.,  etc. 


THIRD  EDITION,  ENLARGED 


NEW  YORK 

SPON  & CHAMBERLAIN,  120  LIBERTY  STREET 
LONDON 

E.  & F.  N.  SPON,  Limited,  57  HAYMARKET,  S.W, 

1918 


CONTENTS 


Introduction 

Page 

Introduction.  The  principle  of  an  electric  bell.  ix 

Chapter  I 

The  Leclanche  cell — Polarization — Setting  up — The 
dry  cell — The  gravity  cell — Connecting  up  cells  . 1 


Chapter  II 

The  single  stroke  bell — The  shunt  bell — The  differen- 
tial bell — The  continuous  ring  bell — The  water- 
proof bell — Forms  of  gongs — The  buzzer — Long 
distance  bells — The  relay — The  push — Three  point 
or  double  contact  push — Floor  push — Door  pull 
— Indicating  push 9 


Chapter  III 

Bell  wires — Joints — Running  wires — How  to  put  up  a 
door  bell — Combinations  of  bells,  pushes  and  bat- 
teries— Faults  in  bells,  faults  in  wiring — How  to 
locate  and  remedy  faults 23 


vi 


CONTENTS 


Chapter  IV 

Page 

Fire  alarms — Thermostats — Metallic  thermostats — Mer- 
cury thermostat — How  to  connect  thermostats — 
Water  level  indicators — Burglar  alarms — Open  and 
closed  circuit  alarms — Window,  door  and  shade 
springs — Alarm  matting — Yale  lock  alarm — Doo 
trip  alarm 40 


Chapter  V 

The  annunciator  drop — The  needle  or  arrow  drop — 

The  pendulum  drop — Wiring  up  annunciators — 
Return  or  fire  call  systems — Double  wire  system — 
Western  Electric  single  wire  system  ....  55 

Chapter  VI 

Three-.wire  return  call  system — Installing  elevator  an- 
nunciators— Burglar  alarm  annunciators — Clock 
alarm  circuit — Bells  for  high  voltages — Bell-ringing 
transformers — Combination  bell,  door  opener  and 
telephone  circuits — Fire  alarm  circuit — interior  fire 
alarm  system — Fire  alarm  system  for  considerable 


areas 


64 


LIST  OF  ILLUSTRATIONS 


Fig.  Page 

1 Electric  bell,  push,  and  battery x 

2 Leclanche  cell 1 

3 Dry  cell 4 

4 Gravity  cell 5 

5 Vibrating  bell 10 

6 Single  stroke  bell 10 

7 Shunt  or  short  circuit  bell 10 

8 Continuous  ring  bell 13 

0 Waterproof  bell 14 

10  Dome  gong 15 

11  Tea  gong 15 

12  Cow  gong 15 

13  Sleigh  bell  gong 15 

14  Spiral  gong 15 

15  Relay  and  circuit  16 

16  Door  push 19 

17  Pear  push 19 

18  Door  push 19 

19  Wall  push 19 

20  Floor  push 20 

21  Door  pull  attachment 22 

22  Wire  joint  first  operation 25 

23  Wire  joint  second  operation 25 

24  Wire  joint  insulating 25 

25  Section  of  house  showing  wiring 29 

26  Bell  with  ground  return 30 

27  Pushes  in  multiple  , 31 


viii  LIST  OF  ILLUSTRATIONS 

Fig.  Page 

28  Bells  in  series 31 

29  Bells  in  multiple 31 

30  Two  bells  and  two  pushes 32 

31  Two  bells  and  two  pushes 32 

32  Two  bells,  two  pushes  and  one  battery  ....  33 

33  Double  contact  push 33 

34  Grounded  bell 34 

35  Tongue  test  of  wiring 38 

36  Knife  test  of  wiring 38 

37  Knife  test  of  wiring 30 

38  Metallic  thermostat 40 

39  Mercury  thermostat 41 

40  Mercury  thermostat  circuit 42 

41  Water  level  alarm 44 

42  Lever  water  level  alarm 45 

43  High  or  low  water  level  alarm 45 

44  Window  spring  for  burglar  alarm 47 

45  Burglar  alarm — closed  circuit 47 

46  Special  bell  connection  for  burglar  alarm  ...  48 

47  Special  bell  connection  for  burglar  alarm  ...  49 

48  Burglar  alarm  and  relay 50 

49  Window-shade  contact  spring 51 

50  House  wired  for  burglar  alarm 52 

51  Door  trip  alarm 53 

52  Annunciator  drop ....  55 

53  Needle  drop 56 

54  Needle  drop  indicating 50 

55  Pendulum  drop 57 

56  Annunciator  drop  circuit 58 

57  Simple  annunciator  circuit 59 

58  Annunciator  and  fire  call  circuit 60 

59  Single- wire  room  and  fire  call 6X 


LIST  OF  ILLUSTRATIONS 


Fig.  -x  Page 

60  Three-wire  return  call  circuit 65 

61  Elevator  bells  and  annunciator  circuit 67 

62  Burglar  alarm  annunciator  circuit 69 

63  Clock  alarm  circuit 71 

64  Bell-ringing  transformer  73 

65  Bell-ringing  transformer  with  three  secondary 

* voltages  73 

66  Western  Electric  interphone  system 75 

67  Western  Electric  interphone  system  for  more  ex- 

tensive service  77 

68  Fire  alarm  circuit 79 

69  Interior  fire  alarm  circuit 81 

70  Fire  alarm  circuit  for  considerable  areas 82 


INTRODUCTION 


An  electric  bell  depends  for  its  action  on  the 
fact  that  a piece  of  iron  wound  with  insulated 
wire  becomes  a magnet  and  will  attract  another 
piece  of  iron  just  so  long  as  an  electric  current  is 
allowed  to  travel  through  the  wire. 

The  instant  the  current  ceases,  the  magnetism 
also  ceases,  and  the  attracted  piece  of  iron  (termed 
the  armature)  is  no  longer  held  in  contact. 

The  general  construction  of  an  electric  bell 
is  shown  in  Fig.  1.  M M are  coils  of  insulated 
wire  wound  on  soft  iron  cores.  A is  a soft  iron 
armature  mounted  on  a flat  spring  so  that  it  is 
normally  kept  a slight  distance  away  from  the 
soft  iron  cores.  5”  is  a brass  screw  with  a plat- 
inum tip  touching  a platinum  disc  on  a spring 
attached  to  the  armature. 

When  the  push  button  P is  pressed  down,  its 
two  brass  springs  touch  each  other,  the  current 
from  the  battery  cell  B then  flows  through  the 
wire  W , through  the  push  P,  through  the 
coils  M M,  along  A to  the  platinum  disc,  out 


INTRODUCTION 


at  S,  which  touches  this  disc,  and  back  to  the 
battery. 

The  instant  this  is  done  the  current  causes  the 
iron  cores  to  become  magnets,  they  attract  A, 
which  then  breaks  contact  at  S'.  The  spring 
mounting  of  A causes  it  to  jump  back  to  its 
first  position,  5*  then  touches  the  platinum  disc 
again,  the  current  flows  as  before,  and  the  arma- 
ture is  again  attracted  only  to  break  contact 
with  S'  and  fly  back. 

This  continual  making  and  breaking  of  the 
circuit  keeps  up  as  long  as  the  push  is  pressed,  a 
ball  mounted  on  A by  means  of  a rod  strikes 
against  the  gong  G causing  a continuous  ringing 
of  the  bell.  The  wires  leading  between  the  bell, 
battery  cell  and  push  must  all  be  insulated,  that 
is,  covered  with  cotton,  rubber,  etc.,  which  pre- 
vents the  leakage  of  current  should  two  wires 
cross  each  other.  Copper  wire  is  mostly  used  for 
circuits  indoors,  the  details  of  the  kind  and  size 
of  wire  will  be  given  later  on. 

The  main  parts  of  an  electric  bell  circuit  are 
then — the  battery  to  supply  the  electric  current; 
the  circuit,  or  wires,  to  carry  this  current ; a push, 
or  circuit  breaker,  to  control  the  current  flow; 
and  a bell  to  utilize  the  current. 


INTRODUCTION 


c- 

I 22 



CHAPTER  I 
The  Battery 


The  Battery  Cell.  The  battery  cell  most  used 
in  electric  bell  work  is  the  Leclanche,  or  some 
modification  of  it. 

The  Leclanche  battery  cell  is  shown  in  Fig.  2, 


Fig.  2 


where  / is  a glass  jar,  Z a rod  of  zinc,  and  P a jar 
of  porous  earthenware  containing  a carbon  rod 
surrounded  by  powdered  carbon  and  peroxide  of 
manganese. 


2 


ELECTRIC  BELLS  AND  ALARMS 


In  setting  up  this  cell  about  four  ounces  of 
sal  ammoniac  (chloride  of  ammonia)  are  put  into 
the  jar  and  enough  water  added  to  come  about 
half  way  up  the  jar. 

The  porous  jar  P and  the  zinc  Z are  then 
inserted,  and  the  cell  is  ready  for  use  in  a few 
minutes  after  the  liquid  has  soaked  through  the 
earthenware  into  the  carbon-manganese  mixture. 
Water  is  often  poured  into  the  porous  jar  through 
holes  in  its  top  to  hasten  this  wetting. 

Wires  are  clamped  by  nuts  or  set-$crews  to  the 
negative  terminal  on  the  zinc  or  the  positive  ter- 
minal on  the  carbon,  it  generally  not  being  of 
consequence  which  terminal  is  attached  to  either 
wire  of  the  circuit. 

A battery  cell  could  be  constructed  without  the 
manganese,  using  simply  a plate  of  carbon  and 
a rod  of  zinc,  but  hydrogen  gas  would  be  gen- 
erated on  the  carbon  plate  when  the  cell  was  work- 
ing and  would  stop  the  current  flowing. 

This  is  called  polarization,  and  peroxide  of  man- 
ganese is  a de-polarizer,  because  it  combines  with 
this  hydrogen  gas  almost  as  fast  as  it  is  generated, 
and  prevents,  to  a great  extent,  the  polarization. 

But  it  does  not  stop  it  entirely,  as  will  be  seen 
if  the  Leclanche  cell  is  kept  working  above  its 
capacity.  Then  the  hydrogen  is  generated  too 
fast  for  the  manganese  to  destroy  it,  and  the  cell 


THE  BATTERY 


3 


ceases  to  work.  In  this  case  a rest  will  often 
restore  the  cell  to  its  former  power. 

Cells  which  have  been  almost  unable  to  make 
a bell  give  even  a single  tap  have  been  found 
good  again  when  allowed  to  remain  at  rest  over 
night. 

In  setting  up  a battery  cell  no  liquid  should  be 
splashed  on  the  brass  terminals  or  corrosion  will 
take  place.  Every  metal  surface  where  connec- 
tion is  made  to  allow  electric  current  to  pass  must 
be  clean  and  bright,  and  all  screws,  or  nuts,  hold- 
ing wires  must  be  screwed  up  tight  so  that  the 
wires  are  firmly  clamped. 

Loose  or  dirty  connections  are  the  cause  of 
probably  eight  out  of  every  ten  troubles  affecting 
bells  and  batteries. 

When  the  fluid  in  a Leclanche  cell  becomes 
milky,  more  sal  ammoniac  must  be  added.  Or, 
better  still,  throw  out  the  old  solution,  wash  the 
porous  jar  thoroughly  in  clean  water,  scrape  the 
zinc  bright,  and  half  fill  the  cell  with  fresh  solu- 
tion. 

The  zinc  wearing  away  rapidly  or  becoming 
covered  with  crystals,  and  a strong  smell  of  am- 
monia, show  generally  that  the  cell  is  being  worked 
too  hard,  or  that  the  current  is  leaking  where  it 
should  not. 

A zinc  rod  in  a cell  working  the  average  door 


4 ELECTRIC  BELLS  AND  ALARMS 

bell  should  last  for  six  months,  the  porous  jar  for 
a year. 

The  Dry  Cell.  The  Leclaiiche  cell  being  a 
cell  with  much  free  liquid  is  liable  to  dry  up  if 
not  watched.  The  dry  cell  (Fig.  3)  is  a modern 


Fig.  3 


form  of  the  Leclanche  where  the  liquid  is  held  by 
an  absorbent  material,  such  as  blotting  paper,  or 
plaster. 

A typical  dry  cell*  is  shown  in  the  figure.  An 


*For  full  description  of  this  class  pf  battery  see  No.  3 
Book  on  “Dry  Batteries.” 


THE  BATTERY 


5 


outside  case  of  zinc  is  lined  with  blotting  paper 
dampened  with  chloride  of  zinc  and  sal  ammoniac. 
A carbon  rod  is  then  inserted  in  the  centre  and 
packed  around  with  carbon  dust  and  peroxide  of 
manganese.  The  latter  mixture  is  also  somewhat 
dampened. 

Molten  wax,  or  a suitable  composition,  is  then 
poured  on  top  of  the  contents  of  the  cell  to  seal  it 
up  and  prevent  the  evaporation  of  the  fluid.  A 


Fig.  4 


terminal  on  the  carbon  rod  and  another  on  the 
zinc  case  complete  the  cell. 

The  voltage  of  both  the  Leclanche  and  the  dry 
cell  is  about  1.45,  when  it  goes  below  this  it  in- 
dicates that  the  cell  is  worked  out. 

The  two  cells  described  are  known  as  open- 
circuit  cells  and  are  only  intended  for  intermittent 
working. 

When  a current  is  needed  for  a long  period  at 
a time  a closed  circuit  cell  should  be  used,  such  as 
the  gravity  Daniell  cell. 


6 


ELECTRIC  BELLS  AND  ALARMS 


The  Gravity  Daniell  Cell.  The  gravity  cell, 
Fig.  4,  has  a zinc  block  Z suspended  from  the 
side  of  the  jar  and  a number  of  copper  leaves  C 
standing  on  edge  at  the  bottom.  A quantity  of 
bluestone  (sulphate  of  copper)  is  poured  over  the 
copper  leaves  and  the  jar  filled  with  water. 

During  the  working  of  this  cell,  copper  is  de- 
posited on  the  copper  plate,  and  sulphate  of  zinc 
formed  at  the  zinc.  To  hasten  the  action  a small 
quantity  of  zinc  sulphate  can  be  added  to  the 
solution  when  setting  up  the  cell. 

The  name  of  this  cell  comes  from  the  fact  that 
the  copper  solution  being  heavier  remains  at  the 
bottom  of  the  jar.  If  the  cell  is  not  worked 
enough,  all  the  solution  will  become  blue  and  the 
zinc  will  blacken.  If  very  dirty  from  this  cause, 
remove  the  zinc,  scrape  and  wash  ‘it  thoroughly. 
Throw  out  all  the  solution,  add  new  sulphate  and 
water  and  replacing  the  zinc,  then  put  the  cell 
on  short  circuit  by  connecting  the  copper  and 
zinc  together  for  a few  hours. 


E.  M.  F.  The  e.  m.  f.  of  a gravity  cell  is  within 
a fraction  of  one  volt,  its  current  nearly  one-half 
ampere. 

Warmth  makes  it  give  a greater  current;  on 
no  account  let  a gravity  cell  freeze. 


THE  BATTERY 


7 


Resistance  of  a Cell.  The  fluids  in  a cell  do 

not  conduct  electricity  as  well  as  copper  does ; they 
offer  more  resistance  and  thus  reduce  the  current 
output. 

The  internal  resistance  of  a cell  may  be  low- 
ered by  using  large  zinc  plates  curled  around  the 
porous  pot. 

The  Samson  cell  has  a large  zinc  plate  bent  in 
the  form  of  a cylinder,  the  carbon-manganese 
combination  standing  in  the  centre  of  it. 

The  dry  cell  also  has  a large  zinc,  the  internal 
resistance  being  thus  much  lowered,  the  current 
output  is  increased.  This  is  by  reason  of  Ohm’s 
law,  which  teaches  that  to  increase  the  current 
flow,  either  the  voltage  of  the  battery  must  be  in- 
creased, or  the  resistance  decreased. 

But  increased  current  means  lessened  life;  there 
is  only  just  so  much  energy  in  a cell  mainly  de- 
pendent on  the  quantity  of  chemicals. 


Grouping  of  Cells.  Cells  may  be  grouped  in  a 
battery  to  get  increased  voltage,  or  increased  am- 
perage. When  connected  for  the  former,  they 
are  in  series,  the  carbon  of  one  is  connected  to  the 
zinc  of  the  next,  and  so  on. 

If  all  the  carbons  are  connected  together  and  all 
the  zincs,  they  are  in  multiple,  and  will  give  the 


8 


ELECTRIC  BELLS  AND  ALARMS 


same  voltage  as -of  one  cell  but  the  combined  am- 
perage of  all. 

In  ordinary  bell  work  the  series  is  the  general 
connection,  the  higher  the  resistance  of  the  cir- 
cuit, or  the  longer  the  wires,  the  more  voltage  is 
required. 


CHAPTER  II 

Bells  and  Pushes 

Electric  Bells.  The  two  main  types  of  house 
bells  are  the  iron  box  and  the  skeleton. 

The  iron  box  has  a cast-iron  frame,  or  base,  and 
a cast-  or  stamped-iron  cover  over  the  mechanism. 

The  skeleton  bell  has  an  iron  frame  but  no 
cover,  and  is  generally  better  finished  and  more 
expensive  than  the  iron  box  bells. 

For  fire  alarm  purposes,  mechanical  bells  or 
gongs  are  made,  in  which  a clockwork  mechan- 
ism causes  the  hammer  to  strike  the  gong  upon 
being  released  by  electromagnetism. 

Marine  or  waterproof  bells  have  an  iron  cover 
fitting  tight  over  a rubber  gasket;  they  are  for 
marine,  or  mining,  work. 

Polarized,  or  magneto,  bells  are  used  in  tele- 
phone work,  and  are  rarely  operated  by  a battery, 
but  have  a miniature  dynamo  generator  operated 
by  hand,  or  power,  to  supply  the  actuating  cur- 
rent. 

Most  bells  are  classed  for  size  by  the  diameter 
of  the  gong,  a four-inch  bell  being  one  with  a 
gong  four  inches  in  diameter;  a six-inch  bell  one 
with  a six-inch  gong,  and  so  on. 


10 


ELECTRIC  BELLS  AND  ALARMS 


According  to  the  use  for  which  they  are  in- 
tended, bells  may  be  vibrating,  as  before  described, 
single-stroke,  shunt  or  short-circuiting,  differen- 
tial, continuous-ringing,  or  adapted  for  circuits  of 
high  voltage. 


The  Single-stroke  Bell.  The  bell  before  de- 
scribed, and  again  shown  in  Fig.  5,  is  a vibrating, 
or  trembling,  bell.  It  is  often  desired  to  have  the 
hammer  give  only  one  stroke  for  each  pressure  of 
the  push,  as  in  signaling  with  a code  of  taps;  in 
this  case  a single-stroke  bell  is  used.  The  circuit 


from  the  binding  posts  is  then  directly  through 
the  magnet  coils  without  any  break  at  the  contact 
screw,  as  in  Fig.  6. 

In  adjusting  such  a bell  to  give  a clear  sound, 
press  the  armature  up  against  the  iron  magnet 
cores  and  then  bend  back  the  hammer  until  it  just 
clears  the  gong.  The  spring  of  the  hammer  wire 
will  carry  the  hammer  sufficiently  forward  to  hit 
the  gong.  The  tone  will  be  clearer  than  if  the 
hammer  dampered  the  gong  by  pressing  against 
it  when  the  armature  was  nearest  the  core. 


BELLS  AND  PUSHES 


11 


By  bringing  out  a third  connection,  a vibrating 
bell  may  be  made  both  single  stroke  and  vibrating. 

The  Shunt  Bell.  There  is  a form  of  bell, 
Fig.  7,  known  as  the  shunt,  or  short  circuit  bell, 
which  is  often  used  when  two  or  more  are  to  be 
connected  in  series,  as  will  be  seen  in  the  descrip- 
tion of  circuits.  In  this  bell  the  circuit  through 
the  magnets  is  not  broken  at  the  contact  screw, 
but  the  forward  movement  of  the  armature  short 
circuits  the  coils. 

As  the  short,  or  shunt,  circuit  is  very  much 
lower  in  resistance  than  the  wire  on  the  magnet 
coils,  the  main  current  flows  around  the  latter  and 
they  do  not  become  energized.  The  sparking  at 
the  shunting  contact  screw  is  much  less  than  it 
would  be  at  the  ordinary  breaking  contact  screw, 
and  the  platinum  points  last  longer. 

The  Differential  Bell.  Sparking  at  the  break- 
ing contacts  of  an  electric  bell  is  detrimental  to 
the  platinum  points,  and  many  remedies  have  been 
devised  to  overcome  it. 

Sparking  is  due  to  the  self-induction  of  one 
turn  of  the  wire  coil  acting  on  its  neighbor,  and 
this  property  is  utilized  in  the  gas  engine,  or  gas- 
lighting spark  coil,  where  a fat  spark  is  needed  to 
ignite  gas. 


12 


ELECTRIC  BELLS  AND  ALARMS 


The  differential  bell  has  two  windings  in  oppo- 
site directions.  The  action  of  one  would  be  to 
produce  an  N-pole  at  one  end  and  an  S-pole  at 
the  other.  But  the  second  coil  produces  poles  just 
the  opposite,  as  the  polarity  of  a magnet  depends 
on  the  direction  in  which  the  current  flows  around 
it. 

Where  the  current  flows  around  the  first  wind- 
ing the  armature  is  attracted  and  its  spring  con- 
tact meets  the  contact  screw  and  allows  the  cur- 
rent to  divide,  part  flowing  through  the  first  coil, 
the  other  flowing  in  the  reverse  direction  in  the 
opposite  way.  One  coil  would  tend  to  produce 
an  N-pole  where  the  other  coil  produced  an  S-pole, 
and  these  opposite  poles  would  so  neutralize  each 
other  that  there  would  be  no  magnetism. 

The  armature  would  therefore  be  pulled  back 
by  its  spring  when  both  coils  were  thrown  into 
circuit.  In  so  doing  it  would  cut  out  one  coil 
and  the  same  series  of  operations  would  recom- 
mence. 

As  a spark  is  normally  produced  where  mag- 
netism is  lost  by  a break  of  circuit,*  no  spark  ap- 
pears, as  magnetism  is  produced  by  a break  of 
circuit  in  this  case. 


*For  a full  explanation  of  self-induction  see  No.  I of 
this  series. 


BELLS  AND  PUSHES 


13 


Continuous-ring  Bell.  In  some  classes  of  bell 
work,  such  as  burglar  alarms,  it  is  desired  that  the 
bell  when  once  started  shall  continue  to  ring  until 
stopped  by  the  person  called.  In  this  case  a con- 
tinuous-ringing bell  is  needed,  such  as  in  Fig.  8. 

When  the  push  P is  pressed,  the  current  flows 


Fig.  s 


in  the  usual  way  through  contact  screw  L,  arma- 
ture spring  A,  magnet  coils  M M,  battery  B,  back 
to  P,  and  the  bell  rings.  But  on  the  first  forward 
movement  of  the  armature  it  releases  the  spring 
contact  S,  which  flies  forward  and  makes  contact 
at  U.  The  circuit  is  now  from  B,  through  M M , 


14 


ELECTRIC  BELLS  AND  ALARMS 


to  A,  thence  through  L and  S,  to  U and  back 
to  B. 

The  bell  will  continue  to  ring  until  the  spring 
contact  .S'  is  moved  back  and  caught  by  the  pro- 
jection on  the  armature  A. 

A continuous-ring  attachment  is  also  made  and 
sold  in  most  electrical  supply  stores,  which  is  com- 
plete in  itself  and  can  be  applied  to  any  bell. 


Fig.  9 


Waterproof  Bells.  In  Fig.  9 is  an  example  of 
a waterproof  bell  where  the  mechanism  is  almost 
all  entirely  encased  in  a waterproof  brass  case. 

The  circuit  is  made  and  broken  inside  the  case, 
but  the  magnet  cores  project  through  it  and  act 
on  a second  armature  placed  outside.  This  sec- 
ond armature  carries  the  hammer  which  strikes 
the  gong  and  is  governed  in  speed  by  the  contact- 
breaking armature  inside. 


BELLS  AND  PUSHES 


15 


Forms  of  Bell  Gongs.  In  order  to  provide  a 
variety  of  sounds,  bells  are  provided  with  gongs 
of  various  shapes. 

Fig.  10  shows  the  ordinary  form  of  gong. 


Fig.  10  Fig.  11  Fig.  12  Fig.  13 


Fig.  11,  a tea  gong;  Fig.  12,  a cow  gong;  and 
Fig.  13,  a sleigh  bell. 

A coil  of  steel  wire  is  also  used,  as  in  Fig.  14, 
which  on  being  struck  by  the  hammer  gives  a 
pleasant  but  not  loud  tone. 


Fig.  14 


The  Buzzer.  The  buzzer  is  the  mechanism  of 
a vibrating  bell  less  the  hammer  and  gong.  As 
the  armature  vibrates  it  makes  a buzzing  noise 
which  does  not  carry  as  far  as  the  sound  from 
a struck  gong.  It  is  used  chiefly  for  a desk  call 


16 


ELECTRIC  BELLS  AND  ALARMS 


and  in  telephone  exchange  work,  or  any  place 
where  general  attention  is  not  desired  to  the  signal. 

Operating  Bells  at  a Distance.  When  it  is 
desired  to  ring  a bell  situated  at  a considerable 
distance  from  the  push,  the  resistance  of  the  line 
becomes  objectionable. 


Fig.  15 


On  lines  of  500  feet,  No.  18  copper  wire  and 
upwards,  the  battery  necessary  would  be  very 
large,  two  small  batteries  and  a relay  would  prove 
more  satisfactory. 

In  Fig.  15  the  circuit  of  a simple  form  of  relay 
is  given.  An  adjustable  contact  screw  C is  placed 
where  an  extension  S'  of  the  armature  A can  strike 


BELLS  AND  PUSHES 


17 


it.  This  extension  is  provided  with  a platinum 
contact.  The  connections  are  as  in  the  figure. 

When  the  push  P is  depressed,  the  current  from 
the  main  battery  M energizes  the  electromagnet  E , 
and  the  armature  A being  attracted,  contacts  5 
and  C meet.  These  contacts  close  the  second  cir- 
cuit containing  the  bell  3 and  the  local  battery  L. 

The  relay  resembles  a second  push  near  the 
bell,  but  controlled  by  current  from  a distance 
instead  of  being  depressed  by  hand.  Its  advan- 
tage consists  in  it  needing  but  a very  weak  cur- 
rent to  move  the  armature  A,  which  is  held  back 
by  a light  spring,  or  by  gravity. 

The  relay  may  then  be  set  near  the  bell  and 
the  wires  from  the  push  may  be  of  a very  great 
length.  Battery  L,  which  actually  rings  the  bell, 
will  thus  only  have  to  work  through  a few  feet 
of  wire. 

Reducing  Resistance  of  a Bell.  Sometimes 
it  is  desired  to  reduce  the  resistance  the  bell  coils 
offer  to  the  current,  the  bell  then  working  over  a 
very  short  line  with  few  cells  of  battery.  Or 
the  bell  coils  may  have  been  wound  with  fine 
wire  for  large  battery  voltage  and  a long  line. 

The  bell  coils  may  be  put  in  multiple,  the  cur- 
rent then  dividing  and  one-half  going  through 
each  spool. 


18 


ELECTRIC  BELLS  AND  ALARMS 


Untwist  the  joint  between  the  spools  near  the 
yoke  or  iron  bar  to  which  the  spools  are  attached. 
Join  one  of  these  ends  to  the  wire  at  the  armature 
end  of  the  other  spool  and  the  second  untwisted 
end  to  the  armature  end  wire  of  its  neighboring 
spool.  Use  short  pieces  of  insulated  wire  for 
these  extra  connections. 

The  current  now  instead  of  having  to  go 
through  one  spool  and  then  the  other,  can  branch 
through  both  at  once. 

The  resistance  to  the  current  of  one  spool  is 
half  the  resistance  of  two,  the  current  through  one 
spool  will  therefore  be  twice  that  through  the 
two  spools  as  at  first  connected.  And  as  there  are 
two  paths  for  it,  each  one-half  the  first  resistance, 
the  total  will  be  only  one-fourth  the  resistance 
of  the  ordinary  series  arrangement. 

The  same  size  battery  will  therefore  send  four 
times  the  current  through  the  spools  in  multiple 
than  when  they  are  in  series. 

It  is  to  be  noted  that  the  wire  on  one  spool  is 
wound  in  the  reverse  direction  to  that  on  the 
other.  The  reason  will  be  apparent  if  the  two 
spools  and  yoke  are  considered  as  merely  one 
spool  bent  in  a U or  horseshoe  form. 

If  both  spools  were  wound  in  the  same  direc- 
tion they  would  be  in  opposite  directions  when  the 
U were  straightened  out,  and  would  cause  like 


BELLS  AND  PUSHES 


19 


poles  at  the  same  ends.  These  poles  would  neu- 
tralize one  another,  so  that  there  would  be  no 
magnetic  attraction. 

This  can  be  readily  proved  by  joining  together 
the  two  yoke  ends  and  the  two  armature  ends  of 
the  spool  wires.  Then  pass  the  current  through 
these  two  joined  connections. 


Fig,  18  Fig.  19 


Fig.  17 


Fig.  16 


The  Push  Button.  Push  buttons,  or  pushes, 
are  made  in  a variety  of  forms,  with  metal,  wood, 
hard  rubber,  or  porcelain  bases. 

Fig.  16  has  a metal  base,  and  is  suitable  for 
a front  door. 

Fig.  17  is  a wooden  pear  push,  and  is  attached  at 
the  end  of  a cord  which  has  the  two  conductors 
braided  in  it,  each,  however,  having  its  own  in- 
sulation. 

Fig.  18  is  a plate  push  for  an  outside  door. 


20 


ELECTRIC  BELLS  AND  ALARMS 


Fig.  19  is  either  of  metal,  wood,  or  porcelain, 
and  is  the  shape  most  commonly  used. 

A three-point  push  has  three  contact  springs. 
One  is  movable  by  means  of  the  button,  one  is 
below  the  movable  spring,  and  the  third  is  above 
it. 


When  the  push  button  is  not  being  depressed, 


the  movable  spring  makes  contact  with  the  upper 
spring.  But  when  the  button  is  depressed,  these 
two  springs  part,  and  the  movable  spring  makes 
contact  with  the  lower  one. 

This  style  of  push  is  used  for  special  bell  and 
annunciator  work,  as  will  be  described  later. 

The  form  of  combination  floor  and  table  push  in 
Fig.  20  is  the  most  solidly  constructed  device  of 
its  kind.  The  lower  part  is  set  in  a hole  bored 
in  the  flooring,  the  metal  flange  keeping  it  in 
place  and  preventing  its  slipping  through. 


. BELLS  AND  PUSHES 


21 


The  floor  push  attachment  works  as  follows : 
The  central  metal  rod  is  divided  into  two  parts 
B Dy  by  an  insulating  piece  of  hard  rubber.  When 
depressed  against  the  action  of  the  spiral  spring 
by  the  foot,  the  upper  part  B connects  together  the 
contact  springs  A C , closing  the  circuit  of  bell 
and  battery.  These  contact  springs  are  insulated 
from  each  other  by  a hard  rubber  block  R. 

From  the  table  push  a cord  containing  two  in- 
sulated wires  leads  to  the  two  parts  of  the  rod 
at  B and  D.  When  the  push  centre  is  pressed 
down,  the  push  springs  come  together  and  practi- 
cally short  circuit  B and  D , which  completes  the 
circuit  of  bell  and  battery.  At  any  time  the  centre 
rod  may  be  removed,  leaving  a surface  almost 
flush  with  the  carpet,  or  floor,  over  which  furni- 
ture may  be  moved  without  injury  to  the  mechan- 
ism of  the  push. 

For  a floor  push  alone  a shorter  form  of  the 
centre  rod  is  also  sometimes  furnished  which  is 
not  divided  by  insulation.  The  spiral  spring 
keeps  it  clear  of  the  lower  contact  A but  enables 
it  to  always  make  connection  with  the  upper  con- 
tact B.  Pressing  this  rod  down  will  also  short 
circuit  the  bell  and  battery  so  that  the  signal  is 
given. 

A door  pull  attachment,  like  Fig.  21,  is  made 
so  that  the  ordinary  form  of  lever  pull  bell  may 


22 


ELECTRIC  BELLS  AND  ALARMS 


be  changed  into  an  electric  bell.  Being  screwed 
up  near  the  door  pull,  a wire  is  run  front  the  lat- 
ter and  fastened  to  lever  L.  When  the  pull  is 
drawn  out  the  lever  L turns  on  a pivot  and  a 
projection  presses  the  insulated  spring  S against 
the  metal  base  B.  The  circuit  of  the  bell  and 
battery  being  thus  closed,  the  bell  rings. 


Indicating  Push  Button.  A push  button  is 
made  which  contains  in  the  base  a small  electro- 
magnet in  series  with  the  line.  An  armature  on 
a spring  is  fixed  near  the  magnet  poles.  When 
the  push  is  depressed,  the  current  travels  through 
this  electromagnet,  and  as  the  circuit  is  made 
and  broken  at  the  distant  bell,  it  is  also  interrupted 
in  the  electromagnet.  The  armature  vibrates  in 
unison  with  the  bell  and  thus  gives  an  audible 
indication  that  the  bell  is  ringing. 


CHAPTER  III 


Wiring , Circuits  and  Troubles 

The  Wire.  The  size  of  the  copper  wire  used 
in  bell  work  is  No.  16,  or  No.  18,  B and  S gauge, 
and  sometimes  smaller,  such  as  No.  20  to  22. 
But  smaller  wire  than  No.  18  has  too  much  re- 
sistance, and  would  necessitate  a larger  battery 
power,  even  if  its  mechanical  strength  were  not 
too  low.  The  insulating  coverings  are  cotton  satu- 
rated with  paraffin  wax  or  compounds. 

The  covered  wires  are  variously  known  as  an- 
nunciator, office,  or  weatherproof  wire,  these  terms 
being  mostly  for  distinction  of  the  coverings  and 
not  for  the  use  to  which  the  wire  would  be  put. 

Annunciator  wire  has  two  layers  of  cotton 
merely  wrapped  around  the  copper  and  then  satu- 
rated with  paraffin. 

Office  wire  has  the  two  cotton  layers  braided, 
the  inside  one  being  filled  with  a moisture-repel- 
ling compound. 

Both  office  and  annunciator  wires  have  their 
outside  coverings  filled  with  paraffin  and  highly 
polished. 

From  the  ease  with  which  annunciator  wire  is 


24 


ELECTRIC  BELLS  AND  ALARMS 


stripped  of  its  cotton  covering,  the  braided  office 
wire  is  to  be  preferred.  These  coverings  are  made 
in  a variety  of  colors. 

Weatherproof  covered  wire  is  mostly  used  for 
electric  light  work,  but  the  sizes  given  above  are 
good  for  bell  work,  although  their  larger  outside 
diameter  makes  them  harder  to  conceal. 

The  approximate  number  of  feet  to  the  pound 
of  office  and  annunciator  wire  is  given  in  the 
table. 


Office 

Wire. 

Annunciator  Wire. 

No. 

Feet  per  lb. 

No. 

Feet  per  lb. 

12 

35 

18 

180 

14 

55 

20 

225 

16 

95 

18 

135 

Joints.  Upon  the  care  with  which  a joint  is 
made  much  depends,  a loose  or  poorly  made  joint 
will  offer  much  resistance  to  the  current. 

The  correct  way  to  start  a joint  in  annunciator, 
or  office,  wire  is  shown  in  Fig.  22.  About  three 
inches  of  each  wire  to  be  joined  is  bared  of  its 
insulation  and  scraped  bright.  The  ends  are  then 


WIRING,  CIRCUITS  AND  TROUBLES 


25 


bent  at  right  angles  to  each  other,  hooked  together 
and  one  end  firmly  twisted  around  the  other,  as 
shown  in  Fig.  23.  Any  projecting  pieces  are  cut 
off,  and  the  joints  should  then  be  soldered  to  pre- 
vent corrosion. 


Fig.  22 


(ZZZZZZZZ 


zzzzzzzzza 


Fig.  23 


a t t / # f .ijy 


Ictzxjez  la 


Fig.  24 


Adhesive  tape  (“friction  tape”)  is  wrapped 
around  the  joint,  Fig.  24,  and  pressed  firmly  to- 
gether so  that  there  is  no  chance  of  its  unravelling. 
The  tape  wrapping  should  extend  across  the  joint 
and  on  to  about  a half  inch  of  the  insulation 
around  each  wire. 


26 


ELECTRIC  BELLS  AND  ALARMS 


Running  the  Wires.  To  detail  all  the  opera- 
tions of  installing  a complex  system  of  bell,  alarm 
and  annunciator  wires  would  be  impossible  from 
the  reasons  that  conditions  vary  and  space  is  lim- 
ited. General  directions  will  then  only  be  given 
to  enable  the  inexperienced  to  run  such  wires  as 
may  be  needed  in  ordinary  domestic  work  and  to 
guard  against  the  most  common  causes  of  failure. 

Wires  may  be  run  in  tin  tubes  to  prevent  the 
depredations  of  rats  and  mice,  or  they  may  be  run 
with  simply  their  own  covering  for  protection ; it 
is  presumed  the  latter  is  undertaken. 

In  a case  where  the  building  is  of  frame  and 
in  course  of  erection  the  task  is  much  simplified. 

Having  first  decided  upon  the  plan,  number  of 
bells,  pushes,  etc.  and  their  location,  proceed  to 
run  the  wires  first  in  order  that  the  pushes,  bells, 
etc.  may  not  be  injured. 

But  where  the  house  is  already  occupied,  as  in 
the  majority  of  cases  likely  to  be  met  with  by  the 
reader,  the  bell  and  battery  may  be  set  first. 

Take  the  case  of  an  ordinary  door  bell  with  the 
push  at  the  front  door,  the  bell  in  the  kitchen  and 
the  battery  in  the  cellar.  If  possible  get  the  wire 
on  two  spools;  it  will  simplify  matters  if  both 
wires  are  of  different  colors.  Starting  at  the  push, 
have  a foot  of  each  wire  for  connection  and  slack, 
and  fasten  each  wire  lightly  to  the  woodwork  with 


WIRING,  CIRCUITS  AND  TROUBLES  27 

staples,  or  double-pointed  tacks,  never  putting  two 
wires  under  one  staple  nor  driving  in  a staple  so 
it  cuts  the  insulation.  Some  cases  will  require  a 
staple  about  every  foot,  on  straight  runs  some- 
times every  three  feet. 

In  many  cases  the  wires  can  be  partly  con- 
cealed in  the  angle  between  a moulding  and  the 
wall,  or  even  in  a groove  of  the  moulding  itself. 
When  running  along  a skirting,  the  wires  may 
often  be  pushed  out  of  sight  between  it  and  the 
floor.  Do  not  attempt  to  draw  the  wires  too 
tight  or  the  changes  of  the  weather  may  break  the 
wires  when  the  woodwork  shrinks  or  swells. 

The  wires  will  be,  one  from  the  push  to  the 
bell,  one  from  the  push  to  the  battery,  and  one 
from  the  bell  to  the  battery.  So  it  is  probable 
that  the  second  wire  can  be  run  right  through  a 
small  hole  bored  in  the  flooring  under  the  push, 
but  inside  the  front  door.  In  this  case  it  will 
be  perhaps  easier  if  the  spool  be  left  in  the  cellar 
and  the  end  of  the  wire  be  pushed  up  from  below 
and  stapled  to  the  woodwork  near  the  push,  leav- 
ing the  cellar  work  to  the  last.  Only  one  wire 
will  be  run  then  direct  to  the  bell  upstairs  and 
it  can  be  better  concealed  than  two. 

If  necessary  it  may  be  drawn  under  a carpet 
and  not  stapled,  or  it  can  often  be  forced  into  the 
crack  between  two  boards,  But  if  not,  run  it 


28 


ELECTRIC  BELLS  AND  ALARMS 


along  the  skirting,  following  the  walls  until  it 
reaches  below  the  bell.  It  is  often  better  to  go 
entirely  around  a room  than  to  cross  below  a 
door. 

If  a door  must  be  crossed  the  wire  may  either 
run  up  one  side  of  the  frame  and  down  the  other 
or  laid  beneath  the  carpet  on  the  sill.  The  former 
is  preferable,  but  takes  more  wire. 

In  many  houses  the  bell  wire  as  well  as  the  bat- 
tery wire  may  be  run  across  the  cellar  beams 
(Fig.  25),  in  which  case  bore  a second  hole  for  it 
near  the  push ; do  not  draw  it  through  the  same 
hole  as  the  push  to  battery  wire.  And,  of  course, 
here  work  upwards  with  the  spool  in  the  cellar. 

Having  reached  the  bell  location,  run  the  third 
wire  down  into  the  cellar  to  the  battery.  Now 
connect  up  the  push,  baring  an  inch  or  so  of  each 
wire,  push  them  through  the  holes  provided  in 
the  push  base,  screw  down  the  push  base  and 
clamp  the  wires  under  the  washers  through  which 
the  connection  screws  run.  Do  this  neatly,  be  sure 
the  ends  of  the  wires  do  not  stick  out,  cut  off 
what  is  left  free  of  the  bared  ends.  Then  con- 
nect the  battery  to  the  wire  from  the  push  and  the 
wire  from  the  bell.  The  last  thing  is  to  scrape 
and  fasten  the  bell  wires  to  the  bell  binding  posts. 
Do  this  so  that  they  cannot  come  loose  and  that 
they  make  good  contact. 


Fig.  25 


30 


ELECTRIC  BELLS  AND  ALARMS 


The  bell  should  now  ring  properly  when  the 
push  is  pressed. 

To  sum  up,  one  wire  leads  from  one  spring 
of  the  push  to  the  bell,  one  wire  from  the  other 
spring  of  the  push  to  the  battery,  and  another  wire 
from  the  remaining  binding  post  on  the  bell  to  the 
remaining  binding  post  on  the  battery.  It  is  im- 
material whether  the  zinc  terminal  or  the  carbon 
terminal  go  to  the  bell  or  push. 

Combinations  of  Bells  and  Pushes.  One  of 

the  wires  in  a bell  circuit  may  be  replaced  by 
the  ground  (Fig.  26).  Connection  may  be  made 
to  a gas  or  water  pipe  or  to  a metal  plate  buried 
deep  in  damp  earth.  Any  wire  fastened  to  such  a 


plate  must  be  thoroughly  soldered  to  it  or  a voltaic 
action  will  be  set  up,  which  will  eat  it  away  at  the 
point  of  contact. 

When  one  bell  is  to  be  rung  from  two  or 
more  points  the  pushes  are  to  be  connected  in 


WIRING,  CIRCUITS  AND  TROUBLES 


31 


multiple  (Fig.  27)  as  if  they  were  in  series;  all 
would  have  to  be  closed  to  complete  the  circuit. 

If  two  bells  are  to  be  operated  from  one  push 


they  may  be  in  series  (Fig.  28),  but  in  this  case 
one  of  them  must  be  arranged  for  single  stroke. 


If  both  were  vibrating  bells  the  armature  of  one 
would  not  vibrate  in  unison  with  the  other  arma- 


ture and  the  result  would  be  irregular  contact 
breaking  and  intermittent  ringing. 

A preferable  connection  for  two  or  more  bells 


32 


ELECTRIC  BELLS  AND  ALARMS 


and  one  push  is  Fig.  29,  where  the  bells  are  in 
multiple.  This  requires  more  current  than  the 
series  method. 


To  ring  two  bells  from  either  one  of  two  points, 
the  arrangement  in  Fig  30  will  answer.  It  re- 
quires only  two  wires  or  one  wire  and  ground 
return,  but  two  batteries.  As  both  bells  are  in 


Fig.  31 


multiple  both  will  ring,  the  one  nearest  the  push 
being  depressed  ringing  the  loudest.  This  is  a dis- 
advantage. If  the  series  arrangement  in  Fig.  31 


WIRING,  CIRCUITS  AND  TROUBLES  33 

be  selected,  one  bell  must  be  arranged  for  single 
stroke.  Both  bells  will  ring  with  equal  power. 

In  Fig.  32  only  the  distant  bell  rings,  the  cir- 


cuit having  only  one  battery  but  three  wires,  or 
two  wires  and  ground  return. 

A plan  where  two  batteries  are  needed  but  only 
two  wires,  or  one  wire  and  ground  is  in  Fig.  33. 


Fig.  33 


here,  making  one  contact  when  depressed  and  a 
second  one  when  not  being  touched. 

In  this  figure  only  the  distant  bell  rings. 


34 


ELECTRIC  BELLS  AND  ALARMS 


Faults  in  Bells.  On  examining  many  electric 
bells  it  will  be  noted  that  only  one  binding  post 
is  insulated  from  the  frame  when  the  latter  is 


Fig.  34 


of  iron  (Fig.  34).  As  the  armature  spring  S'  is  in 
electrical  connection  with  the  frame  F by  reason 
of  its  metal  screws  and  support,  the  circuit  may 
run  from  the  insulated  post  U to  the  magnet  eoils, 
thence  through  the  insulated  contact  screw  C 
through  the  armature  spring  (when  it  is  making 
contact)  and  through  the  frame  to  the  uninsulated 
post  /. 

This  saves  labor,  wire  and  complication,  but  if 
the  insulation  of  the  post  U,  the  wires  W V , or  the 
contact  screw  C be  injured,  the  current  may  take 
a short  path  back  to  the  frame. 

If  C were  thus  grounded,  the  bell  would  act  as 
a single-stroke  bell. 

If  C/  were  grounded,  the  bell  would  not  ring 


WIRING,  CIRCUITS  AND  TROUBLES 


35 


at  all,  as  that  would  be  a short  circuit  on  the  bat- 
tery between  / and  U and  the  latter  would  also 
result  if  the  bare  wire  were  touching  the  frame 
at  V. 

If  the  bare  wire  touched  the  frame  bevond  M M, 
that  is,  along  W,  it  would  be  a single-stroke  bell, 
as  if  C were  grounded. 

As  any  one  of  these  faults  is  likely  to  occur, 
they  should  be  looked  for  when  the  bell  acts  im- 
perfectly, or  not  at  all. 

A very  common  fault  in  a bell  is  when  its  arma- 
ture sticks  to  the  cores  and  thus  does  not  make 
contact  with  the  contact  screw.  This  may  be  from 
a weak  spring  or  because  of  the  loss  of  the  pieces 
of  brass  inserted  in  the  ends  of  the  cores  to  keep 
the  armature  away  from  actual  contact.  A piece 
of  a postage  stamp  stuck  over  the  core  end  will 
often  help  out  in  the  latter  case. 

A high  screeching  noise  from  the  armature  vi- 
brating too  rapidly  but  with  too  little  play,  may 
be  from  excessive  battery  power  or  the  contact 
screw  being  too  far  forward.  The  former  will 
generally  be  detected  by  the  violent  sparking  as 
well  as  the  rapid  vibration. 

In  very  cheap  bells  the  platinum  contacts  may 
be  replaced  by  German  silver  or  some  other  metal. 

Platinum  is  necessary  because  the  sparking 
would  soon  corrode  other  metals,  but  it  is  very 


36 


ELECTRIC  BELLS  AND  ALARMS 


expensive.  To  test  for  platinum  put  a tiny  drop 
of  nitric  acid  on  the  suspected  metal.  If  bubbles 
or  smoke  appear  it  is  not  platinum.  After  apply- 
ing this  test  in  any  case  however,  carefully  wash 
off  and  remove  all  traces  of  the  acid,  as  it  will  cor- 
rode the  metal  into  which  the  platinum  is  riveted. 

Dirty  contacts  will  decrease  the  current  in  the 
bell  coils  and  it  will  not  work  well,  if  at  all. 

Loose  contact  screws  and  wires  also  give 
trouble.  The  adjusting  of  the  contact  screw  is  of 
the  utmost  importance,  and  should  never  be  at- 
tempted'unless  it  is  clearly  necessary. 

Faults  in  Line.  In  looking  for  a fault  in  a 
bell  circuit  make  sure  the  battery  is  working;  if 
only  one  or  two  cells,  put  the  ends  of  two  wires 
attached  to  the  terminals  on  the  tongue : a metallic 
taste  will  indicate  current. 

Then  see  that  the  circuit  wires  are  firmly 
clamped  in  the  terminals  and  no  dirt  or  corrosion 
on  the  connections. 

Next  examine  the  push  button  and  see  that  the 
wire  connections  at  the  springs  are  perfect. 

If  there  is  no  movement  of  the  bell  at  all  when 
the  push  is  pressed  in,  take  a pocket  knife  or 
screw  driver,  and  touch  the  blade  across  the  push 
springs.  If  there  is  current  flowing  sparks  will 
be  seen  when  the  blade  breaks  contact  between 


WIRING,  CIRCUITS  AND  TROUBLES  37 

the  springs.  If  there  are  no  sparks,  detach  the 
wires  from  the  bell  and  twist  the  bare  ends  to- 
gether. Then  try  again  for  sparks — they  may 
now  be  very  minute.  The  tongue  test  is  good  here. 

If  current  is  detected,  examine  the  bell  for  the 
defects  first  mentioned. 

But  if  no  current  is  found  at  the  push  now  the 
wires  are  broken  somewhere. 

First  short  circuit  the  push  springs  by  insert- 
ing a knife  blade  or  piece  of  wire  so  as  to  touch 
both  of  them.  Then  touch  the  two  wires  at  the 
bell,  one  to  each  side  wire  coming  from  the  mag- 
net coils.  If  current  is  up  to  the  bell  and  the  coils 
are  all  right,  a single  stroke  should  result. 

Replace  the  wires  in  the  binding  posts,  clean 
the  platinum  on  both  contact  screw  and  armature 
spring  and  try  the  adjustment.  Troubles  in  the 
bell  will  be  mostly  similar  to  those  before  men- 
tioned. 

If  no  current  has  been  obtained  at  either  bell 
or  push,  and  the  battery  is  in  good  working  order, 
the  line  must  be  tested  for  a cross  or  break. 

If  the  wires  are  touching  each  other  (Fig.  35) 
at  some  bare  spot  S'  between  the  bell  and  the  bat- 
tery, it  will  be  shown  by  the  metallic  taste  upon 
detaching  one  wire  from  the  battery  and  laying 
it  on  the  tongue  T,  together  with  another  wire  W 
from  the  disconnected  terminal  of  the  battery.  The 


38 


ELECTRIC  BELLS  AND  ALARMS 


current  will  travel  from  the  battery  to  the  cross 
at  S,  then  back  along  the  second  circuit  wire  to 
the  tongue  and  through  the  short  wire  to  the 
battery. 


able  that  the  wire  is  broken. 


The  easiest  way  to  find  this  is  to  take  a bell 
to  the  battery  and  connect  it  between  the  circuit 
wires  and  the  battery  (Fig.  36). 

Then  with  a sharp  knife  carefully  cut  away  a 


WIRING,  CIRCUITS  AND  TROUBLES 


89 


little  piece  of  the  insulation  from  each  wire  beyond 
the  bell  and  battery  and  short  circuit  the  bared 
spots  with  the  knife  blade  K.  Keep  working 
towards  the  push.  The  bell  will  ring  each  time 


at  K K until  the  break  D is  passed,  at  C it  will 
not.  It  becomes  an  easy  matter  then  to  locate 
it 

If  the  bell  and  push  are  far  apart,  as  in  Fig.  37, 
a break  between  the  push  and  the  bell  may  be 
found  as  shown.  With  the  knife  blade  K at  differ- 
ent points  the  bell  will  ring,  but  after  passing  the 
break  D it  will  not  ring. 

Such  simple  tests  as  are  here  given  can  be  car- 
ried out  by  any  one,  but  far  better  results  will  be 
obtained  if  the  reason  for  each  is  first  learned. 

This  can  be  readily  done  by  a careful  study  of 
the  diagrams  and  text. 


CHAPTER  IV 
Alarms 


Fire  Alarms.  Thermostats,  heat  alarms  and 
fire  alarms  are  all  practically  the  same,  the  term 
thermostat  being  applied  principally  to  the  appa- 
ratus which  closes  the  electrical  circuit. 


i 

i 

i 

I 

i 

i 


Fig.  38 


Thermostats  act  on  the  principle  that  heat  causes 
expansion  whether  of  substances,  liquids,  or  gases. 

The  degree  in  which  different  substances  ex- 
pand varies  for  the  same  increase  in  temperature. 
This  fact  is  used  in  a common  form  of  thermo- 
stat shown  in  Fig.  38.  A strip  of  wood  or  hard 
rubber  R has  a strip  of  thin  sheet  metal  S riveted 
to  it.  This  compound  strip  is  held  at  one  end  by 


ALARMS 


41 


a lug  L screwed  fast  to  a baseboard.  Upon  an 
increase  of  temperature  the  hard  rubber  expands 
more  than  the  metal  strip  and  the  compound  strip 
bends  towards  the  adjustable  contact  screw  A. 
Upon  touching  the  latter,  the  circuit  through  the 
bell  B,  battery  C and  the  metal  strip  5"  is  com- 
pleted, and  the  bell  rings.  A contact  screw  can 
be  arranged  at  the  other  side  of  S R,  which  will 


give  warning  of  a decrease  in  temperature,  as  the 
rubber  contracts  more  than  the  metal  strip. 

In  some  thermostats  of  this  character  two  metals 
having  different  coefficients  of  expansion,  such  as 
steel  and  brass,  are  used  instead  of  metal  and  hard 
rubber. 

Thermostats  of  this  nature  are  much  used  in 
incubators,  and  they  can  readily  be  combined  with 
electric  apparatus  to  open  or  close  hot-air  valves, 


42 


ELECTRIC  BELLS  AND  ALARMS 


dampers,  etc.,  and  thus  regulate  the  supply  of 
hot  air,  hot  water,  or  gas. 

A thermostat  much  used  in  fire  alarm  work  has 
a thin  metal  chamber  which  is  air  tight.  An  in- 
crease of  temperature  causes'  the  air  to  expand, 
which  swells  out  the  walls  of  the  chamber  and 
closes  an  electric  circuit. 


A 


0^ 

B 

<0 

Q- 

J0 

cp 

i 

i 

<Q 

Fig.  40 


The  mercurial  thermostat  shown  in  Fig.  39  has 
a glass  tube  T and  bulb  containing  mercury.  Into 
each  end  is  sealed  a platinum  wire  P P.  Upon 
the  temperature  rising  to  a predetermined  degree, 
the  expanded  mercury  completes  the  circuit  be- 
tween P P and  the  battery  C and  bell  B are  put 
in  operation. 

Fig.  40  is  the  open  circuit  system  most  used  by 


ALARMS 


43 


the  fire  alarm  companies,  only  one  circuit  of  six 
thermostats  being  illustrated. 

It  will  be  seen  that  if  any  thermostat  closes  the 
circuit  between  the  outer  and  inner  wires  of  the 
ring  A B,  current  will  flow  through  the  corre- 
sponding drop  of  the  annunciator  and  will  attract 
the  armature  A of  the  relay.  This  will  cause  the 
bell  to  ring.  As  the  relay  is  connected  to  the  an- 
nunciator as  before  shown  for  the  annunciator  bell, 
it  offers  a common  path  for  any  drop  to  the  bat- 
tery. Thus  the  bell  will  ring  for  any  circuit,  but 
the  individual  drop  only  will  fall.  In  a simpler 
circuit  the  relay  may  be  dispensed  with  and  a 
vibrating  bell  only  used. 

Thermostats  may  be  operated  on  open  or  closed 
circuits,  that  is,  they  may  give  the  alarm  by  clos- 
ing a circuit  and  ringing  a bell,  or  by  opening  one 
and  releasing  a contact  spring  as  in  the  burglar 
alarm  system  to  be  described  later. 

Water  Level  Alarms.  Where  it  is  desired  to 
signal  the  rising  or  falling  of  water  in  a tank 
above  or  below  a given  point,  a water  level  in- 
dicator as  in  Fig.  41  may  be  used. 

A hollow  ball  H is  mounted  on  the  end  of  a 
rod  which  slides  vertically  in  guides,  not  shown. 
Adjustable  stops  ^ 5 press  against  a spring 
arm  R , pressing  it  up  or  down,  according  as  the 


44 


ELECTRIC  BELLS  AND  ALARMS 


water  level  is  rising  or  falling.  If  rising,  R makes 
contact  with  the  adjustable  screw  A,  if  falling, 
with  D,  in  both  cases  completing  the  electrical  cir- 
cuit of  the  battery  C and  bell  B. 


Fig.  41 


Another  and  simpler  form  is  shown  in  Fig.  42, 
where  the  ball  H is  mounted  on  the  end  of  a 
lever  L pivoted  at  P,  its  rise  or  fall  completing 
the  circuit  of  B and  C as  before. 


ALARMS 


45 


Where  it  is  desired  to  give  a different  signal  for 
the  rise  and  the  fall  of  level,  two  bells  B and  E 


(Fig.  43)  may  be  used  connected  as  shown.  The 
rising  of  the  ball  will  ring  bell  B,  and  its  fall, 
bell  E. 


46 


ELECTRIC  BELLS  AND  ALARMS 


In  both  forms  of  indicator,  a means  must  be 
provided  that  an  undue  rise  may  not  bend  the 
lever.  This  may  be  accomplished  by  using  contact 
springs  instead  of  contact  screws;  it  is,  however, 
then  harder  to  adjust  the  indicator  to  fine  differ- 
ences of  level. 

In  all  cases  the  contacts  must  be  faced  with 
platinum  to  prevent  corrosion. 

Burglar  Alarms.  A burglar  alarm  is  a device 
for  indicating  the  opening  of  a door  or  window, 
by  the  ringing  of  a bell  or  operation  of  an  annunci- 
ator. The  contact  apparatus  at  the  points  to  be 
protected  may  either  open  an  electrical  circuit  or 
close  one,  in  the  latter  case  being  mere  modifica- 
tions of  push  buttons.  The  simplest  form  is  the 
latter  or  open-circuit  method. 

The  spring  contact  to  be  inserted  in  the  door 
jamb  or  window  frame  is  so  constructed  that 
while  under  pressure  the  contacts  are  kept  apart 
and  the  circuit  is  open.  But  when  the  door  or 
window  is  opened,  the  pressure  is  released  and 
a spring  forces  the  contacts  together. 

Fig.  44  is  an  open-circuit  window  spring  fitted 
in  the  window  frame  so  that  when  the  window 
is  closed  the  spring  lug  .S'  is  pressed  inwards, 
breaking  contact  with  the  base  B. 

If  the  window  is  raised,  the  lug  flies  to  the 


ALARMS 


47 


position  shown  by  the  dotted  lines,  and  making 
contact  with  B,  completes  the  circuit  through  bell 
and  battery.  These  springs  are  fitted  in  the  side 


ih_0 

Fig.  44 


of  the  window  frame  in  a vertical  position  and 
are  entirely  concealed  when  the  window  is  shut. 


In  the  closed-circuit  system  the  reverse  hap- 
pens. The  pressure  of  the  closed  door  or  win- 

s 


dow  keeps  the  contacts  together  and  its  opening 
enables  them  to  spring  apart. 

In  Fig.  45  is  a diagram  of  a closed-circuit 
burglar  alarm,  C a cell  of  gravity  battery,  R a 


48 


ELECTRIC  BELLS  AND  ALARMS 


relay,  F the  fixed  contact  and  M the  movable  con- 
tact of  the  spring,  S’  a stud  projecting  through 
the  base  of  the  spring  and  pushed  in  by  the  closed 
door. 

When  the  door  is  closed,  6"  being  pushed  in, 


Fig.  46 


the  circuit  of  C,  R,  F and  M is  closed.  The 
magnets  of  the  relay  hold  the  armature  arm  A 
forward  against  a hard  rubber  contact.  But  when 
S'  is  released,  the  relay  circuit  is  opened,  R loses 
its  power  and  A flies  back,  making  contact,  and 
throwing  in  circuit  bell  B and  battery  L. 


ALARMS 


49 


A form  of  bell  and  relay  combined  is  shown  in 
Fig.  46.  Here  the  armature  A is  held  against  the 
magnets  while  the  circuit  through  the  spring  F 
and  battery  G is  closed.  But  on  opening  this  cir- 
cuit the  armature  flies  back  and  makes  contact 
with  an  adjustable  contact  screw  S'  putting  in 
circuit  a local  battery  C.  The  bell  is  now  practi- 


cally a vibrating  bell;  on  a closed  circuit  it  rings 
until  the  circuit  is  again  closed  or  the  battery  runs 
down. 

A different  connection  of  the  same  scheme  is 
Fig.  47,  where  only  one  battery  is  used.  This 
must  be  a gravity  battery  or  some  other  closed- 
circuit  battery.  The  circuit  can  be  easily  traced 
in  the  figure  and  needs  no  special  description. 


50 


ELECTRIC  BELLS  AND  ALARMS 


Both  of  the  latter  schemes  are  inferior  to  one 
using  a separate  relay.  If  the  circuit  at  the  spring 
were  quickly  closed  again  the  bell  would  either 
stop  ringing,  or  be  so  hampered  as  to  ring  very 
weakly. 


Fig.  48 


A relay  made  as  in  Fig.  48  has  no  spring  sup- 
port to  the  armature  A , which  falls  down  by  grav- 
ity. The  adjustable  contact  C is  screwed  far  back, 
so  that  the  armature  must  fall  a considerable  dis- 
tance away  from  the  electromagnets  before  it 
makes  contact.  This  ensures  that  the  armature 
will  not  be  attracted  and  the  bell  stopped  from 
ringing  by  a re-closing  of  the  circuit  at  the  door 
or  window  spring. 

A shade  spring  (Fig.  49),  is  made  for  either 


ALARMS 


51 


open  or  closed  circuits.  In  operation,  the  shade  is 
pulled  down  and  its  string  or  ring  hooked  on 
to  H.  This  draws  H up  a trifle  against  a spiral 
spring  and’  its  lower  end  makes  contact  with  an 
insulated  spring  5 closing  the  circuit.  If  the 
shade  is  disturbed,  the  spiral  spring  on  the  lower 
part  of  H is  released  and  it  causes  a break  of 
contact  with  in  the  direction  of  the  arrow. 

When  made  for  open  circuit,  ^ is  bent  so  that 


while  under  tension  no  contact  is  made,  but  re- 
lease of  tension  causes  the  contact. 

Fig.  50  gives  the  wiring  of  two  windows  and 
a door  on  the  closed-circuit  system.  It  will  be 
seen  that  the  contact  springs  are  all  in  series, 
opening  a window  or  the  door  will  thus  break 
the  circuit. 

When  setting  the  alarm  at  night  by  connecting 
up  the  batteries,  relay  and  bell,  should  any  one 
of  these  springs  be  open  the  relay  armature  will 
not  hold,  and  the  bell  rings. 


Fig.  50 


ALARMS 


53 


Jn  this  figure  the  relay  is  replaced  by  an  electro- 
magnet holding  up  a drop  shutter  by  magnetic 
attraction.  Upon  the  circuit  opening,  this  shutter 
falls,  exposing  a number  painted  on  it.  At  the 
same  time  it  hits  a spring  contact  placed  below 
it  and  closes  the  bell  and  local  battery  circuit. 

Door  Trip  Alarm.  A swinging  contact  door 
trip  can  be  attached  over  a door  to  ring  a bell 
when  the  door  is  opened. 


Fig.  51 


In  Fig.  51  the  door  trip  is  screwed  over  the 
door  so  that  the  lowest  arm  A is  struck  by  the 
door.  When  the  door  is  opened,  in  the  direction 
of  the  arrow,  the  arm  A is  thrust  forwards,  and  in 
its  turn  moves  the  contact  arm  C,  completing  the 
bell  and  battery  circuit.  But  when  the  door  is 
being  closed,  A swinging  in  the  reverse  direction 
does  not  move  C and  no  alarm  is  given. 


54 


ELECTRIC  BELLS  AND  ALARMS 


Miscellaneous  Alarms.  The  Applegate  elec- 
trical matting  is  composed  of  wooden  slats  with 
springs  so  arranged  that  the  weight  of  any  person 
stepping  on  it  will  close  a circuit  and  ring  a bell. 

It  is  intended  to  be  put  under  the  ordinary  door 
mat  or  under  stair  and  room  carpeting. 

The  Yale  lock  switch  is  a Yale  lock  and  switch 
combined.  Upon  any  key  but  the  right  one  being 
inserted,  a circuit  is  closed  and  an  alarm  bell  is 
rung. 


CHAPTER  V 

Annunciators 

The  Annunciator.  The  mechanism  of  an  an- 
nunciator consists  of  electromagnets  which  allow 
shutters  to  drop  or  needles  to  move  on  the  cir- 
cuits being  closed.  A bell  is  also  rung  in  most 
cases  to  call  attention  to  the  annunciator.  The 
number  of  the  circuit  is  marked  on  the  shutter. 


or  near  the  needle,  either  shutter  or  needle  being 
replaced  by  a reset  device,  which  may  be  mechan- 
ical or  electrical. 

Annunciator  drops  are  made  in  a variety  of 
forms.  Fig.  52  illustrates  the  principle  under- 
lying nearly  all  of  them. 

When  current  flows  through  the  magnet  coils 
M,  the  armature  A is  attracted,  and  being  pivoted 
at  Py  the  lever  hook  H rises  and  allows  the 


56 


ELECTRIC  BELLS  AND  ALARMS 


weighted  shutter  S to  fall  and  display  a number 
painted  on  its  inside  surface. 

The  needle  drop  in  Fig.  53  is  one  that  has  met 
with  great  favor  and  works  as  follows : the  soft 
iron  core  of  the  magnet  C has  a hole  drilled 
through  it,  in  which  turns  the  shaft  S.  An  arrow 
or  needle  is  attached  at  the  front  end  over  the 


face  of  the  annunciator.  A notched  arm  B is 
fixed  on  the  rear  end  of  the  shaft  and  is  held  in 
a horizontal  position  by  the  end  of  armature  A. 

When  the  current  flows  around  C,  armature  A 
turns  on  its  pivot  towards  the  core  of  C,  as  in 
Fig.  54,  unlocking  B,  which  falls  and  thereby 
partly  rotates  shaft  S and  the  arrow'. 

When  it  is  desired  to  reset  the  arrow'  and  arm, 


ANNUNCIATORS 


57 


a button  is  pressed  upwards,  which  raises  a rod 
carrying  an  arm  R.  This  latter  arm  in  turn 
raises  B to  its  former  position,  the  heavy  end 
of  A falls,  and  its  pointed  end  locks  B . 

Pendulum,  or  swinging,  signals  are  used  in  an- 
nunciator work,  where  there  is  a liability  that  the 


Fig..  55 


ordinary  drop  shutter  would  not  be  reset.  They, 
however,  only  give  a visible  signal  for  a few  sec- 
onds, and  are  therefore  liable  to  be  overlooked. 

In  Fig.  55  a pivoted  arm  carrying  a soft  iron 
armature  A and  a thin  plate  B having  a number 
on  it  is  free  to  swing  in  front  of  an  electromag- 
net M . 


58 


ELECTRIC  BELLS  AND  ALARMS 


When  the  current  flows  in  the  electromagnet 
the  armature  is  attracted,  and  upon  the  circuit 
being  broken  at  the  push,  the  armature  is  released 
and  the  arm  swings  to  and  fro. 

The  drops  of  an  annunciator  are  wired  up  as 
in  Fig.  56. 

One  end  of  each  coil  is  attached  to  a common 


return  wire  C,  the  other  end  going  to  the  push  P. 
When  P is  depressed,  the  circuit  of  any  drop  is 
through  M along  C through  bell,  battery  and  up 
common  battery  wire  W back  to  other  contact 
of  push  P.  Depressing  any  push  does  not  there- 
fore affect  any  other  drop  but-  the  one  controlled 
by  it. 


ANNUNCIATORS 


59 


Wiring  up  an  Annunciator.  A diagram  of 
the  connections  for  an  annunciator  with  a separate 
bell  is  given  in  Fig.  57.  Where  the  bell  is  con- 
tained in  the  case  a terminal  will  be  generally 
found  for  connection. 

The  figure  shows  a wire  running  from  the  bat- 
tery to  one  side  of  each  push  button.  This  is  the 
common  return,  or  battery  wire,  and  saves  instal- 


Fig.  57 


ling  two  wires  from  each  push.  It  should  be 
larger,  however,  than  the  rest  of  the  wires,  gener- 
ally about  No.  16  B.  & S. 

All  the  wires  for  an  annunciator  should  be  run 
before  connecting  up.  There  are  different  methods 
of  sorting  out  the  wires  at  the  annunciator.  One 
way  is  to  connect  the  wires  (except  of  course 
common  or  battery  return  wires)  to  the  drops  in 
any  order.  Then  an  assistant  travels  from  push 
to  push  and  presses  each  button,  noting  the 


GO 


ELECTRIC  BELLS  AND  ALARMS 


room  numbers  and  the  order  in  which  they  were 
visited. 

As  each  drop  falls,  its  number  and  order  is 
noted. 

Comparing  this  with  the  list  made  by  the  assis- 
tant will  show  the  correct  changes  to  make. 


Fig.  58 


For  instance,  suppose  pushes  1,  2,  3,  4,  5 and  6 
were  pressed  in  that  order,  and  drops  3,  4,  5,  1, 
2 and  6 fell  in  that  order.  Then  the  wires  at 
the  annunciator  would  be  changed  as  follows: 
From  3 to  1,  4 to  2,  5 to  3,  1 to  4,  and  2 to  5; 
6 would  already  be  in  its  right  place. 

Another  way  is  to  commence  by  twisting  to- 


ANNUNCIATORS 


61 


gether  say  the  wires  at  No.  1 push.  Then  go  to 
the  annunciator  and  touch  each  of  the  push  wires 
to  No.  1 drop  until  it  falls.  Then  connect  it, 
untwist  the  wires  at  No.  1,  push  and  connect  it 
up.  Proceed  to  No.  2 and  so  on  until  all  the 
pushes  have  been  connected  in  turn. 

In  some  cases  it  is  desired  to  answer  back  to 
the  person- calling,  or  to  be  able  to  call  any  person 
from  the  annunciator. 

A circuit  like  Fig.  58  answers  the  purpose  of 
both  annunciator  call  and  return,  or  fire,  call. 
This  requires  two  wires  from  each  room  to  the 
annunciator  and  a common  return  wire.  By  trac- 
ing out  the  circuit  it  will  be  seen  that  when  a 
room  push  is  pressed,  the  annunciator  needle  and 
bell  indicate.  And  when  one  of  the  pushes  near 
the  annunciator  is  pressed,  the  corresponding 
room  bell  rings.  The  former  circuit  is  from  the 
push,  along  the  common  return  wire,  through 
bell  and  annunciator  back  to  the  push. 

The  fire  call  is  from  push  up  line  to  bell  through 
bell  along  common  return  and  through  battery  to 
the  push. 

The  Western  Electric  single-wire  system 
(Fig.  59)  uses  three-point  pushes,  two  batteries 
and  two  return  wires.  Battery  A is  for  the  annun- 
ciator circuit  and  battery  F for  the  fire,  or  return, 
call. 


62 


ELECTRIC  BELLS  AND  ALARMS 


Fift  59 


ANNUNCIATORS 


63 


In  each  room  the  top  contact  and  push  spring 
contact  are  normally  together. 

If  one  of  the  pushes  below  the  annunciator  is 
pressed,  battery  F is  thrown  in  series  with  the 
bell  in  the  room. 

But  when  the  room  push  is  pressed  its  bell  is 
cut  out  and  the  circuit  becomes  like  an  ordinary 
annunciator  circuit. 


CHAPTER  VI 
Annunciators  and  Alarms 

Three  Wire  Return  Call  System.  A three 
wire  return  call  annunciator  system  is  shown  in 
Fig.  60. 

There  are  two  battery  wires  installed,  from 
which  taps  are  taken  off  and  led  to  each  room 
or  push  button. 

Three  way  or  return  call  push  buttons  are 
used  as  shown  at  points  marked  B. 

In  the  diagram,  the  bells  are  marked  A,  the 
drops  in  the  annunciator  D,  the  annunciator  bell 
C and  the  return  call  buttons  in  the  annunciator 
E.  The  batteries  are  as  shown  at  F.  The  heavy 
black  outline  encloses  the  annunciator  mechanism 
and  connections  which  are  drawn  diagrammatically 
for  the  sake  of  clearness. 

Three  stations  only  are  shown  on  the  sketch, 
but  the  annunciators  which  are  manufactured  by 
Edwards  and  Co.,  Inc.,  of  New  York,  are  made 
in  all  standard  sizes. 

Installing  Elevator  Annunciators.  The  install- 
ing of  electric  bells  and  annunciators  in  elevators 
does  not  present  any  special  problems,  although 
the  apparatus  used  must  be  selected  with  a view  to 


64 


FIG.  60 


66  ANNUNCIATORS  AND  ALARMS 

its  being  suitable  to  withstand  the  shocks  incident 
to  elevator  service. 

In  general  the  wires  leading  from  the  push  but- 
tons on  the  different  floors  to  the  bell  or  an- 
nunciator in  the  elevator,  are  flexible  and  made  up 
into  a cable.  One  end  of  this  cable  is  attached  to 
the  underside  of  the  elevator  car,  the  other  end 
being  fixed  usually  to  the  elevator  wall,  at  a point 
midway  between  the  top  and  bottom  of  the  shaft. 

In  Fig.  61  is  shown  a diagram  of  the  general 
circuit  used,  details  of  course  differing  in  each 
installation. 

One  point  to  be  taken  care  of  in  elevator  work 
is  the  attachment  of  the  cables.  The  continual 
movement  tends  to  break  the  wires  at  the  two  ends 
if  good  flexible  cable  is  not  used  and  the  installa- 
tion done  in  a workmanlike  manner. 

Elevator  cable  is  a standard  article  and  may  be 
procured  through  any  electrical  ; supply  store. 
That  most  commonly  used  consists  of  the  requisite 
number  of  copper  conductors  each  composed  of 
16  strands  No.  30  B.  and  S.  gauge  soft  and  un- 
tinned copper  wire.  These  flexible  conductors  are 
insulated  with  two  reverse  wrappings  of  cotton  and 
one  braid  of  cotton.  The  insulated  conductors 
are  cabled  together  with  a steel  supporting  strand 
where  extra  tensile  strength  is  required,  as  in  the 
case  of  extra  long  cables.  The  number  of  con- 
ductors generally  ranges  from  3 to  20  inclusive. 

The  wires  leading  from  the  push  buttons  to  the 
cable  should  be  preferably  rubber  covered  and 


CABLE 


68 


ANNUNCIATORS  AND  ALARMS 


braided.  Only  where  economy  at  the  outset  is  de- 
sired may  ordinary  annunciator  or  office  wires  be 
employed. 

A connection  block  carrying  binding  posts  is 
used  at  each  point  where  the  cable  connects  to  the 
push  button  wires  or  to  the  annunciator.  This  may 
be  home-made  or  purchased  ready  made,  as  desired. 

Burglar  Alarm  Annunciators.  Although  almost 
any  annunciator  may  be  used  for  open  circuit 
burglar  alarm  work,  they  usually  do  not  contain 
certain  devices  which  are  desirable  in  burglar  alarm 
work. 

In  Fig.  62  is  shown  a diagram  of  a burglar  alarm 
annunciator,  the  view  being  schematic  of  the  back 
board. 

The  references  are  as  follows:  A is  the  main 
alarm  bell  situated  wherever  desired  and  connected 
to  the  binding  posts  BB.  The  battery  connection 
leading  directly  to  the  battery  K is  marked  C 
and  that  leading  to  the  contact  spring  is  marked 
D.  The  cut-off  switch  E cuts  off  the  battery  while 
F is  the  constant  ring  switch.  G is  the  upper  bar 
and  H the  lower  bar,  while  the  letters  JJ  denote 
the  indicating  drops.  The  door  and  window  springs 
are  lettered  5'.  At  L is  a switch  which  may  be 
used  to  disconnect  the  entire  burglar  alarm  sys- 
tem. Where  it  is  desired  to  disconnect  only  a sec- 
tion at  a time,  the  switch  corresponding  to  the 
section  is  turned  off  the  upper  bar  G and  cn  to  the 
lower  bar  H . 


FIG.  62 


70 


ANNUNCIATORS  AND  ALARMS 


Clock  Alarm  Circuit.  A diagram  of  the  wiring 
and  connections  on  the  back  board  of  all  clock 
alarms  is  illustrated  in  Fig.  63.  This  diagram 
embodies  the  principles  of  the  last  described  circuit, 
but  includes  the  circuit  of  a clock-operated  alarm. 

Bells  for  High  Voltages.  The  use  of  electric 
bells  on  lighting  circuits  is  becoming  quite  general, 
as  it  obviates  the  necessity  of  using  batteries,  and 
thereby  simplifies  both  installation  and  maintenance. 

There  is  no  fundamental  objection  to  operating 
make  and  break  bells  on  electric  light  circuits.  Pro- 
viding the  voltage  and  amperage  are  the  same, 
there  is  little  difference  between  the  current  from 
a direct-current  dynamo  and  that  from  a battery. 
But  owing  to  the  higher  voltages  of  the  lighting  cir- 
cuit over  that  generally  employed  from  batteries, 
the  bell  coils  must  be  wound  to  high  resistance^  to 
keep  down  the  current  strength.  There  are  also 
other  slight  changes  to  assist  in  suppressing  spark- 
ing, as  have  been  already  treated  on. 

Where  the  circuit  is  not  over  220  volts,  the  bells 
are  wound  with  fine  wire  and  have  also  self-con- 
tained resistance  coils.  For  500  volts  and  over,  a 
resistance  lamp  is  connected  in  with  the  bell  which 
in  this  case  is  wound  for  a 150-volt  circuit. 

These  bells  up  to  6-inch  and  inclusive  will  operate 
on  circuits  of  either  direct  or  alternating  current. 

Above  this  size  it  is  necessary  to  use  specially 
constructed  bells  on  alternating  current  circuits. 

Most  large  hotels  and  office  buildings  having 


FIG.  63 


72 


ANNUNCIATORS  AND  ALARMS 


direct  current  lighting  service  are  using  it  for  ring- 
ing bells  and  similar  work  to  the  total  exclusion 
of  batteries. 

Where  the  number  of  units  to  be  operated  justi- 
fies it,  motor  generators  are  operated  in  connection 
with  the  lighting  mains  to  produce  a low  voltage 
most  suitable  for  the  bells.  The  connections  in 
this  case  are  no  different  to  those  when  batteries 
are  employed. 

Bell-ringing  Transformers.  The  best  system 
for  operating  bells  and  annunciators  from  alternat- 
ing current  circuits  is  undoubtedly  that  employing 
small  specially  constructed  transformers  to  reduce 
the  voltage.  These  transformers  are  being  used 
universally  for  hotel  and  office  work  where  alternat- 
ing current  is  available.  They  are  simple,  being 
merely  one  or  more  coils  of  well  insulated  wire 
wound  on  soft  iron  cores  and  having  connections 
for  both  the  lighting  circuit  and  the  bell  circuit. 

As  a general  rule  the  coils  are  divided  as  to  their 
number  of  turns  or  according  to  the  ratio  of  trans- 
formation desired.  For  example,  if  the  circuit 
were  110  volts  and  10  volts  was  required  for  the 
bell  circuit,  the  total  number  of  turns  in  the  trans- 
former would  be  connected,  1%1  to  the  lighting  cir- 
cuit and  Yu  to  the  bell  circuit. 

The  bell-ringing  transformers  on  the  market  are 
made  in  several  styles.  One  small  style,  Fig.  64, 
for  single  residences,  is  for  use  on  110  volts  and 
produces  a bell  voltage  or  secondary  voltage  as  it 


ANNUNCIATORS  AND  ALARMS 


FIG.  64 


FIG.  65 


BELL-RINGING  TRANSFORMERS. 


74 


ANNUNCIATORS  AND  ALARMS 


is  termed,  of  6 volts.  Another  size,  Fig.  65,  of  this 
transformer  has  three  secondary  voltages  6,  12  and 
18,  each  of  which  can  be  used  by  connecting  to  the 
right  binding  posts. 

It  is  to  be  noted  that  where  the  lighting  service 
voltage  or  primary  voltage  varies  from  the  above, 
the  secondary  voltage  delivered  to  the  bell  circuit 
will  vary  in  like  proportion.  It  should  also  be  noted 
that  a careless  reversing  of  the  connections,  that 
is  connecting  the  secondary  leads  to  the  light- 
ing circuits,  instead  of  the  primary  leads  would 
cause  a like  high  voltage  at  the  other  terminals  of 
the  transformer,  raising  it  in  due  proportion  in- 
stead of  lowering  it.  Thus  such  carelessness  would 
produce  a voltage  of  2,400  volts  instead  of  6 if  a 
transformer  intended  to  deliver  6 volts  from  a 120- 
volt  circuit  was  wrongly  connected. 

The  results  might  very  well  then  be  dangerous. 
All  transformers  are  properly  marked,  however, 
and  such  an  error  only  occurs  through  ignorance  or 
carelessness. 

The  installation  of  these  bell-ringing  transformers 
is  simplicity  itself ; they  require  no  care  after  in- 
stallation and  have  met  with  the  approval  of  the 
National  Board  of  Fire  Underwriters. 

Combination  Circuits.  Circuits  intended  pri- 
marily for  electric  bells  or  annunciators  in  houses 
and  apartments  may  often  be  also  made  to  serve 
for  other  electrical  devices  such  as  door  openers, 
house  telephones,  etc.  This  subsidiary  apparatus 


76 


ANNUNCIATORS  AND  ALARMS 


may  be  installed  with  a little  additional  wiring  or 
perhaps  will  not  need  any  other  wires,  as  when 
both  the  devices  are  not  used  at  once. 

Electrical  door  openers  are  great  conveniences 
and  are  practically  indispensable  where  the  outside 
door  is  on  another  level  to  the  location  of  the 
dweller  or  where  two  or  more  families  occupy  the 
same  house.  The  device  is  simple,  consisting  of  an 
electrically  released  spring-plate  against  which  the 
lock  bolt  is  normally  held  and  a door  opening  spring. 

When  the  door  opener  button  is  pressed,  the 
spring  plate  is  released,  releasing  the  lock  bolt  by 
the  same  action.  The  door  spring  then  forces  the 
door  open  enough  to  clear  the  opener  plate,  which 
flies  back  into  position  when  the  button  is  released. 

These  door  openers  are  made  in  several  forms 
for  door  frames,  such  as  those  on  thin  doors,  iron 
gates,  for  surface  or  rim  locks,  for  thick  doors, 
sliding  doors  and  any  other  regular  type  of  door. 

‘The  push  button  is  the  same  as  used  for  electric 
bells  and  may  be  located  wherever  desired.  The 
pushes  are  wired  in  multiple  as  shown  in  Figs.  66 
and  67,  which  are  two  circuits  of  a type  of  the 
Western  Electric  interphone,  a system  of  house 
telephones  supplied  for  houses  and  buildings-  of 
every  size.  Fig.  66  shows  a circuit  which  provides 
telephone  service  between  the  vestibule  and  the 
apartments,  the  door  opener  wiring  being  clearly 
indicated.  In  Fig.  67  the  circuit  provides  a more 
extensive  service,  enabling  the  janitor,  the  apart- 
ments and  the  tradesmen  to  intercommunicate  in 


FIG.  67 


78 


ANNUNCIATORS  AND  ALARMS 


the  most  desirable  system.  The  door  opener  wiring 
is  also  deafly  shown. 

The  convenience  of  having  telephone  connection 
in  the  house  or  hotel  and  its  advantages  over  speak- 
ing tubes  are  ’too  well  known  to  need  extended 
comment.  Where  electric  bells  have  already  been 
installed  it  is  quite  feasible  now  to  use  the  same 
wires  for  telephones  also. 

Telephone  sets  especially  designed  for  this  serv- 
ice are  manufactured  by  the  Western  Electric  Com- 
pany in  their  interphone  series.  They  are  simple 
and  compact,  and  may  be  installed  by  anyone  who 
can  put  up  an  electric  bell. 

Fire  Alarm  Circuits.  A fire  alarm  circuit  suit- 
able for  factories,  private  plants  or  groups  of 
buildings  is  shown  in  Fig.  68.  It  is  a series  system, 
with  closed  circuit,  the  gongs  sounding  whenever 
the  circuit  is  opened  whether  by  the  contact  breaker 
in  the  boxes  or  by  the  accidental  breaking  of  a wire. 
This  insures  that  it  remains  in  good  working  order, 
as  when  any  part  of  the  circuit  is  opened,  a warn- 
ing tap  is  sounded  on  every  bell  or  gong. 

The  boxes  have  contact  breakers  which  send  a 
separate  number  of  impulses  for  each  box,  thus  an- 
nouncing the  box  number  on  each  gong.  The  boxes 
and  gongs  may  be  located  anywhere,  as  the  system 
is  perfectly  flexible. 

The  reference  letters  in  the  diagram  are  as  fol- 
lows: C indicates  the  gongs  which  are  preferably 
of  the  electro-mechanical  type,  a coiled  spring  pro- 


80 


ANNUNCIATORS  AND  ALARMS 


viding  force  for  the  blow,  electricity  being  merely 
used  to  release  and  retain  the  hammer  or  striker. 
The  alarm  boxes  are  marked  BB  and  the  battery 
which, is  of  the  closed  circuit  type  is  marked  D. 

Interior  Fire  Alarm  System.  Another  system 
suitable  more  particularly  for  indoor  operation  is 
illustrated  m Fi'g.  69.  Here  the  alarm  is  given  by 
breaking  the  glass  front  of  an  alarm  box  and  re- 
leasing or  pressing  an  electrical  contact. 

The  box  sounded  indicates  by  causing  a drop  to 
fall  on  an  annunciator  and  at  the  same  time  rings 
an  alarm  bell.  The  latter  are  generally  provided 
with  constant  ring  attachments,  which  keep  the 
bell  sounding  until  shut  off. 

The  annunciator  shown  in  the  diagram  has 
switches  for  controlling  each  individual  bell  circuit, 
and  also  for  control  of  the  entire  system. 

There  is  no  practical  limit  to  the  number  of  sta- 
tions in  this  system,  it  being  determined  by  the  size 
of  the  annunciator  used  or  by  other  obvious  factors. 

The  reference  letters  on  the  diagram  are  as  fol- 
lows : A,  alarm  bells  which  may  be  located  where- 
ever  desired.  B,  break-glass  alarm  boxes  also  lo- 
cated at  convenient  points.  C,  annunciator  drops, 
D,  switches  on  annunciator  which  control  each  in- 
dividual bell  circuit,  enabling  any  circuit  to  be  cut 
out,  cut  in  or  tested  without  disturbing  any  other 
circuit.  £ is  a general  alarm  switch,  causing  all 
bells  to  ring  at  once  when  it  is  operated. 

The  battery  F varies  with  the  number  of  bells  and 


FIRE  ALARM  SYSTEMS 


81 


boxes  and  the  length  of  line,  from  three  cells  up- 
wards. A cut-out  switch  H is  added  to  cut  out 
the  entire  system  by  opening  the  battery  wire. 


y ( 

ri 

D ( 

i - f 

J o 

i 

4>(k 

c 

■<fc 

>(S) 

•fl1,  1 

L_ 

f L 

~'0 — o 

c 

FIG.  69 


The  annunciator  bell  is  at  /,  an  auxiliary  bell  being 
added  in  multiple  with  it  when  necessary. 


’ 3 f 

9 

9 

0 ( 

3 .( 

3 < 

FIG.  70 


fiHMW 


FIRE  ALARM  SYSTEMS 


83 


Fire  Alarm  System  for  Considerable  Areas. 

Where  the  area  is  more  extensive  and  the  number 
of  stations  considerable,  the  system  illustrated  in 
Fig.  70  is  very  suitable.  It  consists  of  the  requisite 
number  of  break-glass  boxes,  bells  and  a more 
elaborate  annunciator  system.  In  general  details  it 
resembles  the  last  system,  but  uses  a relay  to  send 
out  the  current  for  ringing  the  alarm  bells. 

When  a box  operates,  the  current  impulses  sent 
on  the  line  act  on  the  relay  instead  of  directly  on 
the  bells.  Each  stroke  of  the  relay  closes  a local 
circuit  which  includes  the  bells  and  the  battery. 

This  system  does  away  .with  large  batteries  and 
is  very  enconomical  of  wire.  The  current  needed 
for  the  relay  is  very  small,  whereas  in  a direct  sys- 
tem of  any  size,  the  current  and  voltage  to  ring  a 
number  of  bells  located  at  wide  intervals  would  be 
prohibitive. 

The  reference  letters  are  as  follows:  AA  are 
the  alarm  bells,  BB  the  break-glass  alarm  boxes, 
C is  the  annunciator  bell,  D is  the  relay  which  re- 
mains closed  when  an  alarm  comes  in  keeping  the 
bells  constantly  ringing  until  shut  off.  £ is  a re- 
sistance coil  and  F is  the  battery. 

A system  cut-out  switch  G and  JJ  switches  on 
the  annunciator  for  controlling  individual  circuits 
are  also  provided.  HH  are  the  annunciator  drops 
and  K is  a constant-ring  switch  which  can  also  be 
used  for  a general  alarm  to  ring  all  the  bells  at 
once. 


SELENIUM  CELLS 

THE 

Construction,  Care  and  Use  of  Selenium 
Cells  with  Special  Reference 
to  the  Fritts  Cell 


By ' 

Thomas  W.  Benson 

The  lack  of  definite  information  relative  to  the 
construction  of  Selenium  Cells  has  led  the  writer  to 
record  the  results  of  some  of  his  experiments  and 
to  fully  describe  the  apparatus  as  developed  by  him. 

Contents  of  Chapters 

1.  Selenium  The  Element 

2.  Consideration  of  Cell  types  and  their 
Characteristics;  The  Bildwell  Cell; 
The  Ruhmer  Cell;  The  Mercadier 
Cell;  The  Bell  and  Taintor  Cell; 
The  Gripenberg  Cell 

3.  Construction  of  Fritts  Selenium  Cells 

4.  Testing  and  Maturing  Selenium  Cells 

5.  Applications  of  Selenium  Cells 

6.  The  Care  of  Selenium  Cells 

73  pages,  15  diagrams  and  3 halftone  page  plates, 
734  x 534  inches.  Cloth,  $1.50 


Everybody  Wants  This  Book. 


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13  NEW  DESIGNS 


